Method for creating, updating, and recording seamless presentation information of moving picture data in a rewritable recording medium

ABSTRACT

This invention provides a method for creating, updating, and recording information for seamless presentation of moving picture data in a rewritable recording medium. When recording moving picture data on a rewritable recording medium, seamless presentation information, a part of navigation data, is recorded along with the picture data for seamless presentation of the recorded picture data. The method for creating and recording seamless presentation information of the present invention can effectively reduce the amount of created seamless presentation information by omitting some fields of the seamless presentation information when they are unnecessary. If some video objects of recorded picture data are erased, navigation data related to the removed video objects should be erased and seamless presentation information should also needs proper modification. The method for updating and recording seamless presentation information of the present invention enables effective management of seamless presentation information by updating seamless presentation information related to the video object following erased video objects.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a method for creating,updating, and recording seamless presentation information of movingpicture data in a rewritable recording medium, and more particularly,but not by way of limitation, to a method for creating seamlesspresentation information with no unnecessary information fields and foreffectively updating seamless presentation information when some videoobjects are erased.

2. Description of the Related Art

Optical disks have come into wide use since the advent of compact disc(CD) and the demand for optical disks is expected to grow steadily withpopularization of digital versatile disk (DVD). Optical disks includeread-only disks such as CD-ROM and DVD-ROM, write-once disks such asCD-R and DVD-R, and rewritable disks such as CD-RW and DVD-RAM. Thespecification of DVD-RTRW, which is standard writing/reading format of arewritable disc, has not released yet and standardization for theDVD-RTRW is under way.

As rewritable optical disks like DVD-RAM are of immensely largecapacity, users may store a variety of data such as moving pictures,still pictures, audio data, and the like on a single recording medium.Each time a new data file is recorded on a rewritable recording medium,navigation information for locating the data file after recording iscreated and recorded along with the data file on the recording medium.The recorded navigation information is referred to whenever the relevantdata file is accessed.

Navigation information regarding all data files stored on a recordingmedium is contained in a navigation data table as shown in FIG. 1, whichis recorded as a single navigation data file on the recording medium.Accessing the recording medium entails loading the navigation data fileinto a memory, wherein the navigation data reside all the time. Whenrecording a moving or still picture on the recording medium, the area inwhich the picture file will be recorded is determined with reference tothe navigation information. Recording a picture file always accompaniescreating management information regarding the recorded picture file andupdating the navigation data file to include the newly createdmanagement information.

Management data pertaining to moving pictures comprise movie videoobject information (M_VOBI) and movie video object presentation orderinformation (Cell Information or simply CI). Suppose that a movingpicture file is composed of n movie video objects (M_VOBs) M_VOB#1˜M_VOB#n as shown in FIG. 2. Then, n M_VOBIs (M_VOBI#1˜M_VOBI#n in FIG.2) and n CIs (CI#l, CI#2, CI#4, . . . shaded in FIG. 2) corresponding tothe n M_VOBs are created in the same order that the n M_VOBs arerecorded. The created M_VOBIs and CIs are stored in the movie A/V fileinformation table (M_AVFIT) and the original program chain informationtable (ORG_PGCIT) of the navigation data shown in FIG. 1, respectively.

When the recording medium is accessed, the navigation data file is readfrom the recording medium and loaded into a memory as mentioned before.If reproduction of a moving picture is requested, M_VOBIs and CIsrelevant to the requested moving picture file are read from the M_AVFITand ORG_PGCIT of the navigation data table, respectively. In referenceto the obtained M_VOBIs and CIs, the requested moving picture file canbe located from the recording medium and reproduced.

As shown in FIG. 1, the movie A/V file information table (M_AVFIT)comprises movie A/V file information table information (M_AVFITI)wherein information on the M_AVFIT such as the end address of theM_AVFIT is stored and movie A/V file information (M_AVFI#1). TheM_AVFI#1 further comprises movie A/V file general information (M_AVFGI)wherein general information on the M_AVFI such as the number of M VOBIscontained in the M_AVFI is stored and M_VOBIs, M_VOBI#1˜M_VOBI#n. Eachof M_VOBIs comprises movie VOBI general information (M_VOBIGI) whereinthe ID code of the relevant VOB is stored, movie VOB stream information(M_VOB_STI) wherein video and audio attributes of the relevant VOB isstored, seamless presentation information (SMLI) wherein information forseamless presentation of successive MOVs (M_VOB#i and M_VOB#i+1, i=1˜n)is stored, and time map information (TMAPI) wherein information forspecial playback or time search is stored.

A moving or still picture file is recorded on the recording medium as agroup of video objects (VOBs). For reproducing moving picture datareceived and recorded as successive data stream, it is necessary topresent the relevant VOBs seamlessly. On the other hand, seamlesspresentation is not always necessary for moving picture data obtainedthrough repeated recording-stop process. If successively inputtedpicture data contain still pictures as well as moving pictures, thepicture data are recorded being classified into movie VOBs (M_VOBs) andstill picture VOBs (S_VOBs). In this case, seamless presentation betweenthe group of M_VOBs and the group of S_VOBs is not necessary, either.

When recording received picture data on the recording medium, it istherefore necessary to create information on whether to presentsuccessive VOBs forming the picture data seamlessly so that theinformation can be used in the course of data reproduction. Suchinformation is recorded in the SMLI of the navigation data table shownin FIG. 1.

As shown in FIG. 1, the SMLI comprises a seamless presentation flag(SML_FLG) which indicates how to present the relevant VOB after thepreceding VOB is presented (for example 1 indicates seamlesspresentation is needed, while 0 indicates seamless presentation is notnecessary), the presentation start time of the first video field of therelevant VOB (VOB_V_S_PTM), the presentation end time of the last videofield of the relevant VOB (VOB_V_E_PTM), system clock reference (SCR) ofthe first pack of the relevant VOB (VOB_FIRST_SCR), system clockreference of the last pack of the preceding VOB (VOB_LAST_SCR), VOBaudio stop time (VOB_A_STP_PTM) which denotes pause time of audio atdiscontinuity in RTRW's PTM describing format between the current VOBand the preceding VOB, and VOB audio gap length (VOB_A_GAP_LEN) whichdenotes the discontinuity period at discontinued point between thecurrent VOB and the preceding VOB.

As depicted in FIG. 3, a M_VOB is composed of a plurality of videoobject units (M_VOBUs), each of which comprises a plurality of videopacks (V_PAKs), subpicture packs (SP_PAKs), and audio packs (A_PACKs).

The V_PAKs of each M_VOB are coded by MPEG-2 video encoding method. Thefirst V_PAK comprises a pack header, a system header, a packet header,and video data as shown in FIG. 4A, while each of the other V_PAKscomprise a pack header, a packet header, and video data as shown in FIG.4B. The system clock reference (SCR) and presentation time stamp (PTS)needed for presentation of the video pack are recorded in the packheader and packet header, respectively.

The A_PAKs of each M_VOB are coded by one of the following encodingmethods: linear PCM coding as shown in FIG. 5A, Dolby AC-3 coding asshown in FIG. 5B, and MPEG-2 audio coding as shown in FIG. 5C. Withoutregard to the adopted encoding method, the SCR and PTS are recorded inthe pack header and packet header, respectively.

A M_VOB comprises multiple top fields (or even fields) and bottom fields(or odd fields) as shown in FIG. 6, and a pair of top and bottom fieldsforms a frame. The PTS of the first field of the M_VOB amounts to thepresentation start time of the VOB (VOB_V_S_PTM) and the sum of the PTSof the last field and {fraction (1/60)} sec amounts to the presentationend time of the VOB (VOB_V_E_PTM).

As mentioned earlier, seamless presentation of audio and video data maynot be necessary provided the moving picture is taken through repeatedrecord-stop process or the picture data contain both moving and stillpicture data. In such cases, therefore, the fields of VOB_FIRST_SCR andVOB_LAST_SCR in the SMLI are unnecessary since such fields are utilizedonly for seamless presentation of successive VOBs.

In conventional navigation data structures, whether the fields may benecessary or not, every SMLI contains the fields of VOB_FIRST_SCR andVOB_LAST_SCR, which unnecessarily increases the amount of navigationdata. Moreover, when some VOBs are erased from picture data, the SMLI ofthe VOB following the removed VOB should be appropriately dealt with,which has not been sufficiently considered.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodfor creating and recording seamless presentation information needed forseamless presentation of successive video objects of moving picturedata, which reduces the amount of resulting seamless presentationinformation data.

It is another object of the present invention to FM provide a method forupdating and recording seamless presentation information when some videoobjects of recorded moving picture data are deleted, which enableseffective management of seamless presentation information data byappropriately updating the navigation data related to the video objectfollowing the erased video objects.

The method for creating and recording seamless presentation informationof the present invention comprises the steps of recording picture databeing received on the recording medium by grouping the data into videoobjects; determining whether to specify two successive video objects asa pair of video objects to be presented seamlessly; and setting aseamless presentation flag contained in seamless presentationinformation of the latter of the two successive video objects dependingupon the determination result, and creating optional information fieldsin the seamless presentation information based on the seamlesspresentation flag value.

The method for updating and recording seamless presentation informationof the present invention comprises the steps of erasing video objectsasked to be deleted; and updating seamless presentation information ofthe video object following the erased video objects.

These and other objects of the present application will become morereadily apparent from the detailed description given hereinafter.However, it should be understood that the detailed description andspecific examples, while indicating preferred embodiments of theinvention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention and wherein:

FIG. 1 is a table showing a structure of conventional navigation datafor managing picture data recorded on a rewritable recording medium;

FIG. 2 is a schematic diagram illustrating the process of creatingnavigation data when recording moving picture data on a rewritablerecording medium;

FIG. 3 is a schematic diagram showing the structure of movie videoobject shown in FIG. 2;

FIGS. 4A and 4B are schematic diagrams showing the structure of a videopack shown in FIG. 3;

FIGS. 5A, 5B, and 5C are schematic diagrams showing the structure of anaudio pack shown in FIG. 3;

FIG. 6 is a schematic diagram to explain video presentation start time(VOB_V_S_PTM) and end time (VOB_V_E_PTM) of a video object;

FIGS. 7A and 7B are schematic diagrams showing the structure of seamlesspresentation information according to an embodiment of the presentinvention;

FIG. 8 is a schematic diagram of an optical disk recording/reproducingapparatus embodying the present invention;

FIG. 9 is a flow chart showing the method for creating and recordingseamless presentation information of moving picture data in a rewritablerecording medium according to an embodiment of the present invention;and

FIG. 10 is a flow chart showing the method for updating and recordingseamless presentation information of moving picture data in a rewritablerecording medium according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be described indetail referring to the accompanying drawings.

FIGS. 7A and 7B show the seamless presentation information (SMLI) of thenavigation data according to an embodiment of the present invention.

FIG. 7A depicts the SMLI wherein the SML_FLG is 0 indicating thatseamless presentation of successive video objects is not needed. SuchSMLI can be created when moving picture data are obtained in one placeand obtained again in another place after a time interval, or movingpicture data and still picture data are received successively.

FIG. 7B depicts the SMLI wherein the SML_FLG is 1 indicating thatseamless presentation of successive video objects is required. Whenmoving picture data are received and recorded as successive data streamwith no additional time gap, the relevant VOBs need seamlesspresentation. In this case, the SMLI shown in FIG. 7B is created.

As depicted in FIGS. 7A and 7B, the method for creating seamlesspresentation information of moving picture data according to anembodiment of the present invention creates SMLI of a differentstructure depending on the value of the SML_FLG. If the SML_FLG of SMLIis 0, then the VOB_FIRST_SCR and VOB_LAST_SCR of the SMLI are not neededso such fields are not created. As a result, the fields of VOB_FIRST_SCRand VOB_LAST_SCR are created only when the SML_FLG is 1, therebyreducing the amount of seamless presentation information contained inthe navigation data.

FIG. 8 shows a schematic diagram of an optical diskrecording/reproducing apparatus embodying the present invention.

The apparatus comprises an optical pickup 10 for recording/reproducinginformation on/from a recording medium OD, an analog signal processingunit 20 for filtering and digitizing high-frequency analog signalsreproduced from the recording medium OD and converting digital data tobe recorded on the recording medium OD into analog signals, a digitalsignal processing unit 30 for decoding and encoding digital data andyielding a control signal for data synchronism, an A/V data processingunit 40 for decoding audio/video input data, hereinafter referred tosimply as A/V data, and encoding audio/video input signals into A/Vdata, a control unit 50 for controlling general operation of theapparatus in response to a user's requests, and a plurality of memoriesM1, M2, and M3 for storing temporary data created in each signalprocessing phase. All these components are operatively coupled. Thenavigation data file is loaded into the memory M1.

When recording a moving picture data on the recording medium OD in theapparatus shown in FIG. 8, first of all the control unit 50 loads thenavigation data file recorded on the recording medium OD into the memoryM1. Referring to the loaded navigation data, the control unit 50 recordsthe picture data on the recording medium OD and creates managementinformation regarding the recorded picture data. The created managementinformation is added to the navigation data file loaded in the memoryM1.

The moving picture data are recorded on the recording medium as a groupof video obejcts (M_VOB#1˜M_VOB#n shown in FIG. 2). The video objectinformation M_VOBIs (M_VOB#1˜M_VOBI#n shown in FIG. 2) are created inthe same order of M_VOBs. Also cell information CIs (Cell#1, Cell#2,Cell#4, . . . shown in FIG. 2) are created also in the same order andthe created CIs are recorded sequentially in the original program chaininformation table (ORG_PGCIT) of the navigation data table shown in FIG.1.

Suppose that in FIG. 2, Cell#l, Cell#2, Cell#2, . . . Cell#n are relatedto moving picture data, while Cell#3 is related to still picture data.Then VOBIs, M_VOBI#1 and M_VOBI#2, are information on M_VOB#1 and MVOB#2 recorded successively on the recording medium. The SML_FLG of theSMLI of VOBI#2, therefore, is set as shown in FIG. 7B and the first SCRof M_VOB#2 and the last SCR of the preceding VOB, M_VOB#1 are recordedin the fields of VOB_FIRST_SCR and VOB_LAST_SCR of M_VOB#2,respectively.

In contrast, M_VOB#2 and M_VOB#3 are not recorded in succession sincethere is a still picture video object (not shown in FIG. 2) recorded inbetween. Hence, M_VOB#3 does not need to be presented seamless after thepreceding still picture video object is presented. As a result, theSML_FLAG of the SMLI of M_VOBI#3 is cleared and the SMLI does notcontain the fields of VOB_FIRST_SCR and VOB_LAST_SCR as shown in FIG.7A.

Provided a user records moving picture data and resumes recording ofmoving picture data after a time interval, the SMLI of the first M_VOBIof the newly recorded picture data does not include the fields ofVOB_FIRST_SCR and VOB_LAST_SCR as shown in FIG. 7A since the SML_FLG ofthe SMLI is 0. Decision about whether to create the fields or whether toset the SML_FLG is made by the control unit 50.

Even though recording of moving picture data is resumed after a timeinterval, the previously recorded data and newly recorded data can bepresented in succession if the user requests seamless presentation. Thecontrol unit 50 tests if the user chooses the recording mode whichrequests seamless presentation of moving picture data when resumingrecording. If so, the control unit 50 sets the SML_FLG of the firstM_VOBI of newly recorded picture data and creates SMLI with the fieldsVOB_FIRST_SCR and VOB LAST_SCR. The first SCR of the current VOB isrecorded in the VOB_FIRST_SCR and the last SCR of the preceding VOB isrecorded in the VOB_LAST_SCR.

If a request to erase a VOB, say VOB#i, is received, the control unit 50erases the VOBI and CI corresponding to the VOB and erases the VOB fromthe recording medium. And then, the control unit 50 updates navigationinformation of the M_VOB following the removed VOB. More specifically,the SML_FLG of M_VOBI#(i+1) is cleared and the VOB_FIRST_SCR andVOB_LAST_SCR fields are removed from the VOBI. In addition, the fieldsof VOB_A_STP_PTM and VOB_A_GAP_LEN are updated.

The method for creating and recording seamless presentation informationof moving picture data in a rewritable recording medium according to anembodiment of the present invention is explained below in detail withreference to the flow chart shown in FIG. 9.

Referring to FIG. 9, if recording of moving picture data has beenrequested, the control unit 50 begins execution of a recording controlroutine, loading the navigation data file from the recording medium intothe memory M1 (S31). Also, the control unit 50 controls the A/V dataprocessing unit 40, the digital signal processing unit 30, and theanalog signal processing unit 20, so that the moving picture obtainedfrom an external device is recorded on the recording medium OD (S33).

The input data are recorded on the recording medium OD as a series ofM_VOBs. The control unit 50 creates M_VOBIs corresponding to the VOBsand adds the M_VOBIs to the M_AVFIT of the navigation data loaded in thememory M1. The SML_FLG of the first M_VOBI is 0 and the SMLI does notcontain the fields of VOB_FIRST_SCR and VOB_LAST_SCR, because the firstVOB needs not to be presented seamlessly with the last M_VOB of thepreviously recorded picture data. Also, the control unit 50 creates CIscorresponding to the recorded VOBs and adds the CIs to the ORG_PGCIT ofthe navigation data stored in the memory M1 (S35).

Continuing at step S37, the control unit 50 tests if the currentoperating mode is for recording still picture data (S37). If not, as instep S33, the control unit 50 controls each system component so thatmoving picture input is recorded on the recording medium OD (S39). Thereceived picture data are grouped into M_VOBs, and M_VOBIs regarding theM_VOBs are created and added in the M_AVFIT of the navigation data inthe memory M1. The M_VOBs need to be presented seamlessly with thepreceding M_VOBs because the moving picture data are obtainedsuccessively after the previously obtained moving picture data arerecorded. Therefore, unlike step S35, the SML_FLG of the newly createdM_VOBI is 1 and so the fields of VOB_FIRST_SCR and VOB_LAST_SCR arecreated and recorded in the SMLI. Also, the control unit 50 creates CIsregarding the recorded VOBs and adds the CIs to the ORG_PGCIT of thenavigation data stored in the memory M1 (S41).

At step S43, the control unit 50 tests if end of the recording mode hasbeen requested. If not, program control returns to step S37 wherein itis tested whether recording of still picture data has been requested.Unless requested, program control returns to step S39 and the aboveprocedure is repeated. If a request has been received, step S47 isreached and recording of input still picture data begins. As in case ofmoving picture data, still picture data are recorded as a series ofVOBs. After the first VOB of the input picture data is recorded, thecontrol unit 50 creates a S_VOBI related to the first VOB and adds theS_VOBI to the S_AVFIT of the navigation data loaded in the memory M1.Also, the control unit 50 creates a CI regarding the recorded VOB andadds the CI to the ORG_PGCIT of the navigation data stored in the memoryM1 (S49). The control unit 50 examines if end of the recording mode hasbeen requested (S51). If not, program control returns to step S53wherein it is tested whether recording of moving picture data has beenrequested. Unless requested, program control returns to step S47 and theabove procedure is repeated. If a request has been received, programcontrol returns to step S33 and steps S33 through S35 are repeated. Inthis case, the first VOB of new moving picture data does not needseamless presentation, and so the VOBI relevant to the VOB includesSMLI, SML_FLG of which is 0 as shown in FIG. 7A.

Meanwhile, end of recording mode has been requested at step S43 or S51,the control unit 50 copies the navigation data in the memory M1 to therecording medium OD and finishes control operation (S45)

The method for updating and recording seamless presentation informationof moving picture data in a rewritable recording medium according to anembodiment of the present invention is explained below in detail withreference to the flow chart shown in FIG. 10.

In response to a user's request, the control unit 50 begins execution ofan erasing control routine, loading the navigation data file from therecording medium into the memory M1 (S61). Suppose that VOB#i is to bedeleted. The control unit 50 reads navigation information VOBI#i relatedto VOB#i from the M_AVFIT or S_AVFIT. Referring to the information, thecontrol unit 50 removes VOB#i from the recording medium OD.

Subsequently, the control unit 50 removes VOBI#i related to the deletedVOB#i from the M_AVFIT or S_AVFIT and removes CI related to the deletedVOB#i from the ORG_PGCIT.

The control unit 50 accesses M_VOBI#(i+1) to clear the SML_FLG of theSMLI, remove the fields of VOB_FIRST_SCR and VOB_LAST_SCR, and updatethe fields of VOB_A_STP_PTM and VOB_A_GAP_LEN (S67). As M_VOB#i iserased from the recording medium, continuity between M_VOB#(i+l) andM_VOB#(i−1) does not hold and seamless presentation is not needed. Thisis why the SML_FLAG of M_VOB#(i+1) is cleared.

At step 69, the control unit examines if the erasing mode ends. If not,program control returns to step S63. If so, the control unit 50 copiesthe navigation data in the memory to the recording medium, therebycompleting the erasing control routine (S71).

The invention may be embodied in other specific forms without departingfrom the sprit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description and all changeswhich come within the meaning and range of equivalency of the claims aretherefore intended to be embraced therein.

What is claimed is:
 1. A method for creating a seamless presentationinformation structure for picture data, the method comprising the stepsof: (a) grouping picture data into video objects; (b) determiningwhether to specify two successive video objects as a pair of videoobjects to be presented seamlessly; (c) setting a seamless presentationflag contained in seamless presentation information of one of the twosuccessive video objects based the determination result; (d) determiningwhether or not to create certain information fields pertaining toseamless operation in the seamless presentation information, dependingon the value of the seamless presentation flag; and (e) selectivelycreating said information fields in the seamless presentationinformation based on said determining (d) results.
 2. A method accordingto claim 1, wherein said data grouping is performed based upon whetheror not the picture data are received consecutively.
 3. A methodaccording to claim 1, wherein said data grouping is performed based uponthe type of the picture data being received.
 4. A method according toclaim 3, wherein said type of the picture data is classified by whetherthe data being received are moving picture data or still picture data.5. A method according to claim 1, wherein said step (b) comprises thesteps of: comparing types of the two successive video objects; anddetermining whether to specify the two successive video objects as apair of video objects to be presented seamlessly based on the comparisonresult.
 6. A method according to claim 5, wherein said type of videoobject is classified by whether the video object is related to movingpicture data or still picture data.
 7. A method according to claim 1,wherein, in said step (d), said information fields include at least onefield of system clock reference.
 8. A method according to claim 7,wherein said at least one field of system clock reference comprises thelast system clock reference field of the former of the two successivevideo objects and the first system clock reference of the latter of thetwo successive video objects.
 9. A method according to claim 1, wherein,in the step (e), the seamless presentation flag has two possible values,and wherein said information fields pertaining to the seamless operationare created to exist in the seamless presentation information if theseamless presentation flag has a first value, and said informationfields pertaining to the seamless operation are not created to exist inthe seamless presentation information if the seamless presentation flaghas a second value.
 10. A method according to claim 9, wherein, in saidstep (e), said information fields include a last system clock referencefield of the former of the two successive video objects, and a firstsystem clock reference field of the latter of the two successive videoobjects.
 11. An apparatus for creating a seamless presentationinformation structure for picture data, the apparatus comprising: meansfor grouping picture data into video objects; means for determiningwhether to specify two successive video objects as a pair of videoobjects to be presented seamlessly; means for setting a seamlesspresentation flag contained in seamless presentation information of oneof the two successive video objects based the determination result;means for determining whether or not to create certain informationfields pertaining to seamless operation in the seamless presentationinformation, depending on the value of the seamless presentation flag;and means for selectively creating said information fields in theseamless presentation information based on the result of determiningwhether or not to create said information fields.
 12. An apparatusaccording to claim 11, wherein said means for grouping groups said databased upon whether or not the picture data are received consecutively.13. An apparatus according to claim 11, wherein said means for groupinggroups said data based upon the type of the picture data being received.14. An apparatus according to claim 13, wherein said type of the picturedata is classified by whether the data being received are moving picturedata or still picture data.
 15. An apparatus according to claim 11,wherein said means for determining whether to specify the video objectsincludes: means for comparing types of the two successive video objects;and means for determining whether to specify the two successive videoobjects as a pair of video objects to be presented seamlessly based onthe comparison result.
 16. An apparatus according to claim 15, whereinsaid type of video object is classified by whether the video object isrelated to moving picture data or still picture data.
 17. An apparatusaccording to claim 11, wherein said information fields being selectivelycreated include at least one field of system clock reference.
 18. Anapparatus according to claim 17, wherein said at least one field ofsystem clock reference comprises the last system clock reference fieldof the former of the two successive video objects and the first systemclock reference of the latter of the two successive video objects. 19.An apparatus according to claim 11, wherein the seamless presentationflag has two possible values, and wherein said information fieldspertaining to the seamless operation are created to exist in theseamless presentation information if the seamless presentation flag hasa first value, and said information fields pertaining to the seamlessoperation are not created to exist in the seamless presentationinformation if the seamless presentation flag has a second value.
 20. Anapparatus according to claim 19, wherein said information fields includea last system clock reference field of the former of the two successivevideo objects, and a first system clock reference field of the latter ofthe two successive video objects.
 21. A method for managing seamlesspresentation information of moving picture data in a rewritablerecording medium, comprising the steps of: (a) erasing video objectsrequested to be deleted; and (b) updating seamless presentationinformation of the video object following the erased video objects. 22.A method according to claim 21, wherein said step (b) updates a seamlesspresentation flag in the seamless presentation information of the videoobject following the erased video objects.
 23. A method according toclaim 21, wherein said step (b) erases a field of system clock referencecontained in navigation information for the video object following theerased video objects.
 24. A data structure usable in recording seamlesspresentation information of picture data in a recording medium, the datastructure comprising: navigation information pertaining to data filesstored on the recording medium, the navigation information includingseamless presentation information pertaining to seamless operation ofthe picture data, the seamless presentation information including aseamless presentation flag which indicates whether or not a seamlesspresentation is needed, and certain information fields existing ornon-existing in the seamless presentation information depending on thevalue of the seamless presentation flag, said certain information fieldspertaining to a seamless operation.
 25. A data structure according toclaim 24, wherein, if the seamless flag has a first value, then saidcertain information fields do not exist in the seamless presentationinformation.
 26. A data structure according to claim 25, wherein, if theseamless presentation flag has a second value, then said certaininformation fields exist in the seamless presentation information.
 27. Adata structure according to claim 25, wherein the first value of theseamless presentation flag is “0”.
 28. A data structure according toclaim 26, wherein the second value of the seamless presentation flag is“1”.
 29. A data structure according to claim 26, wherein said certaininformation fields include system clock reference fields pertaining tothe seamless operation.